Crystallization process



Patented Oct. 16, 1962 3,059,008 CRYSTALLIZATION PROCESS Fredric J. Baur, Cincinnati, Ohio, assignor to The Procter ggamble Company, Cincinnati, Ohio, a corporation of o No Drawing. Filed Sept. 8, 1961, Ser. No. 136,733 11 Claims. (Cl. 260-420) This invention relates to an improved crystallization process. More particularly, it relates to the addition of certain crystal modifying agents to glyceride oils containing fatty materials which are insoluble in the oils, whereby separation of the insoluble fatty materials from the oils is facilitated.

A large amount of vegetable glyceride oil is used as salad oil. Such oils can serve as a base for various liquid salad dressings, providing an oily coating for salad ingredients. They are also used in mayonnaise emulsions. Both salad oils and mayonnaise are usually kept under refrigeration by the housewife. At temperatures of about 40 F. or lower, fatty materials will deposit out of many salad oils, causing them to have a cloudy appearance. In mayonnaise, such crystal formation tends to break the emulsion, causing separation of fatty material from the aqueous portion.

If soy bean oil is used as a salad oil it tends to develop a characteristic beany odor and flavor. Even when it has been rendered completely odorless and fiavorless by high-temperature steam deodorization, the characteristic odor and flavor will return, in part, at least, due to the linolenic acid content of the oil.

It has been proposed that the stability of soybean oil against odor and flavor reversion can be increased by hydrogenation. However, hydrogenation decreases the unsaturation of unsaturated component fatty acids and also converts the unsaturated acids to higher-melting and less soluble isomers. The oil must then be winterized by a process including cooling and subsequent separation of insoluble glycerides to remove materials which will solidify when the oil is refrigerated, and thereby cause undesirable salid oil performance and appearance. Other oils such as cottonseed oil are given a similar Winterizing treatment. Insoluble fatty materials in oils such as corn oil are also removed by a cooling step, followed by a separation step.

Another important use of glyceride oils is in the paint industry. Oils of particular interest are the so-called drying oils which form protective coatings because of the ability of these oils to polymerize or dry after they have been applied, thereby forming tough, adherent, impervious and abrasion-resistant films. It is generally believed that the film-forming properties of drying oils are related to their degree of unsaturation, and that the films are formed by polymerization of double bonds present in unsaturated oils. It is highly desirable, therefore, that oils suitable for use as drying oils contain a large amount of triunsaturated glycerides, and relatively few trisaturated glycerides or mixed saturated-unsaturated triglycerides.

US. Patents 2,442,531 and 2,442,533, issued to E. W. Eckey on June 1, 1948, disclose the directed rearrangement of soybean oil to form an improved drying oil. By means of the process disclosed in these patents a substantial portion of the mixed saturated-unsaturated triglycerides in soybean oil is rearranged to form a larger proportion of highly saturated glycerides and highly unsaturated glycerides. The more saturated glycerides in crystalline form are then separated from the rearranged mixture, leaving an unsaturated oil very suitable for use as a drying oil.

Special coating fats are required for coating of candies.

These fats must have a high melting point so that they will not be greasy at normal room temperatures. However, these fats must also melt in the mouth when the candy is eaten, and thus the presence of fats melting at too high temperatures are undesirable. When oils such as hydrogenated palm kernel oil and palm oils, either hydrogenated or unhydrogenated, are to be used for this purpose, it may be desirable to separate out highly-sat urated materials which would produce a waxy taste in the mouth. Suitable Confectioners fats can also be formed from the more saturated portions or" directed rearranged triglycerides.

At times it would be desirable to use palm oil as a major constituent of a margarine oil. In certain geographic locations palm oil is cheaper than other oils, and a supply of palm oil may be more readily available than a supply of some other oil. It has been found that the content of high-melting insoluble fats in palm oil at a temperature of 92 F. is too high to produce a satisfactory margarine, since these insoluble fats will impart a waxy taste in the mouth during eating. Separation of the insoluble fats from palm oil would increase its utility as a margarine constituent.

One of the main problems encountered in the separation of insoluble fatty materials from glyceride oils has been the fact that the insoluble fatty materials entrain a large amount of glyceride oil. In addition, conventional separation procedures are very slow.

it has now been found that by the process of this invention the separation of insoluble fatty materials from liquid glyceride oils is greatly facilitated, thereby permitting the recovery of a much larger amount of liquid oil than has heretofore been possible. In addition, the rate of separation is greatly increased. As used herein the term insoluble fatty materials is intended to include materials which dissolve in oils at elevated temperatures and which will precipitate out of solution as the oils are cooled and allowed to stand.

It is therefore an object of this invention to provide a process for modifying insoluble fatty materials in glyceride oils whereby the subsequent separation of the fatty materials is greatly facilitated.

It is a further object of this invention to provide an improved process for making a salad oil.

Another object is to provide an improved method of making a drying oil.

Yet another object is to provide a method of making confectioners fats which have good eating quality.

Other objects and advantageous features will be apparent from the following detailed description.

In general, the process of this invention comprises the steps of dissolving, in a glyceride oil containing insoluble fatty material, at a temperature at which substantially all of said fatty material is in solution in said glyceride oil, from 0.001% to 1.0%, by weight of oil, of dextrin esteritied with an average, per glucose unit, of at least one saturated fatty acid having from 13 to 22 carbon atoms in the alkyl chain and from 0 to 2 saturated short chain fatty acids having from 1 to 5 carbon atoms in the alkyl chain; cooling the glyceride oil to a temperature at which insoluble fatty material comes out of solution; and separating the insoluble fatty material from the oil. The dextrin ester exerts a modifying effect on the insoluble fatty material so that it comes out of solution in the form of large crystalline aggregates. These entrain a smaller amount of liquid fatty glycerides during separation than do crystals formed in the absence of ester.

The process of this invention is generally applicable to any glyceride oils which contain fatty materials which will dissolve in the oils at elevated temperatures and .temperature for 35 minutes.

Washed, and dried.

- 3 which will crystallize out subsequently cooled and allowed to stand. For example, the removal of insoluble fatty materials from oils which are conventionally winterized to form salad oils, such as cottonseed oil, hydrogenated soybean oil, and corn oil, is greatly facilitated The process can be applied to oils such as palm oil and palm kernel oil, either hydrogenated or unhydrogenated, to form improved margarine oils or confectioners fats.

Directed rearranged triglycerides can also be processed by this invention. Preferably the directed rearrangement is carried out as described in US. Patent 2,442,531, issued June 1, 1948, in which triglyceride oils are contacted with a low temperature molecular rearrangement catalyst at such a temperature that the more highly-saturated triglycerides are precipitated as they are formed during the rearrangement of the glycerides in the oil. A list of suitable rearrangement catalysts is set forth in the aforementioned U.S. Patent 2,442,531. However, it is'to be understood that other suitable rearrangement catalysts and operating conditions can be used. As used herein the term directed rearrangement is intended to denote,

of solution when the oils are 7 andshort-chain acids. Such a process is disclosed in US. Patent 1,959,590, issued May 22, '1934. Other methods, such as reaction of dextrin with acid chlorides arealso suitable, and it is to be understood that the invention is not limited to any particular method of preparation of the dextrin ester.

It is preferred that the oils tobe processed be heated to a temperature at which substantially all of the insoluble fatty material is in liquid form prior to slowly cooling the oil in which is dissolved the dextrin ester. The ester can be added prior' to or after heating. The exact conditions for coolingwill vary with the amount of oil in the batch and the amount of insoluble fatty material, but the optimum cooling conditions can be determined by those skilled in conventional oil 'graining procedure.

the rate of filtration decreased to 1 drop per 10 seconds. This was selected as representing substantial completion of filtration. The filtration time to reach this point was recorded, and the filter cakes were weighed. The following results were noted:

As can be seen from the above data, the'addition of dextrin esters tothe soybean oil resulted in a great decrease in filtration time. Also, the amount of entrained oil in the filter cake Was greatly reduced as shown by the comparison of weights of the filter cake.

Improved filtration can also be achieved by' using other additives such as dextrin tripalmitate; Corresponding dex-trin esters, including those of myristic, stearic, arachidic, and behenic acids, or mixtures of these acids with each other or with palmitic acid, can be substituted in the foregoing examples with comparable results. it is also possible to substitute propionic, butyric, valeric, or caproicacid residues, or mixtures of these in place of or in addition to acetic residues, and in combination withthe long-chain acids. The use of from 0.001% to 1.0% of any of these esters will provide quicker and more effective separation of the solids from directed rearranged soybean oil. It should be appreciated that dextrin esters used in the practice of this invention usually will be a mixture of various esters and that the specified An ester of dextr in containing about 1 /2" acetic acid groups and 1 /2 palmitic groups, per glucose unit, was

dissolved in three pound batches refined cottonseed oil at levels of 0.01%, 0.03%, and 0.05%. Each batch was v heated to a temperature of about 130 F., and then Q The insoluble'fatty materials are conveniently sepa rated by conventional filtration procedures, but other methods of separation such as centrifuging, can be used. The improved results which can be achieved' by the process of this invention are clearlyillustrated by the following examples:

' EXAMPLE I V 1600 grams of refined and bleached soybean oil containing 0.5% of sodium methoxide as a rearrangement catalyst Was heated to 120 F. and maintained at that The sodium methoxide was in the form of a suspension in xylene prepared by the gradual addition, during vigorous agitation, of an-' Testing samples were prepared by placing 100 grams of the rearranged oil in containers together with dextrin esters 'in the amounts indicatedy The'fatty aci'd'portion of these esters is defined in terms of the molecules of fatty The oil mixture was then cooledto 40 F. and held at that temperature for 48 hours without agitation. Each sample was then filtered through paper in .a Buchner funnel under a vacuum of 6 to 9 mm. mercury absolute. The following data were obtained:

1 Yield of on Filtration Amt. AddltnretPercent) (Percent) Rate b/hr.)

It will be noted that the yield of oil Was better, and also that the filtration rate was greatly increased. EXAMPLE in A interizing treatment similar to that of Example II was used on soybean oil which had been hydrogenated to an iodine value of about 10 5; The following data were acid per glucose unit'of 'th'e dextrin. The samples were Other oils such as corn oil and directed" rearranged glyceride oils can be substituted in the foregoing examples with comparable results. i i

The practice of the process of this invention in the removal of fatty materials which are insoluble in glyceride oils at higher temperatures is illustrated by the foll wing example:

EXAMPLE IV Soybean oil was hydrogenated to an iodine value of 105 and winterized by holding it at 50 F. for two weeks and holding it at 40 F. for three days. The oil was then vacuum filtered. A mixture was formed containing 95% of the clear oil filtrate and 5% of a saturated triglyceride containing about 2 palmitic acid groups and 1 stearic acid group per molecule. This saturated triglyceride had an iodine value of 0.012. To the mixture was added 0.1%, by weight, of a dextrin esterified with about 1 /2 acetic acid groups and 1 /2 palmitic acid groups per glycose unit. A second sample was prepared containing 0.1%, by weight, of dextrin tripalmitate. 250 gm. samples of each of these mixtures, together with a sample without added ester, were heated to 140 F. for one hour to destroy all crystal nuclei and then cooled to 80 F. and held at that temperature for three days to permit crystals to form. The resulting mixtures of insoluble fatty material and glyceride oil were filtered through a Buchner funnel using filter paper and vacuum. The following measurements were recorded of the total amounts of oil passing through the filter at various time intervals.

Comparable results will be achieved by substitution in the foregoing examples of oils such as directed rearranged glyceride oils, hydrogenated vegetable oils and other glyceride oils Containing fatty materials insoluble in these oils at higher temperatures.

Although it is to be understood that the invention is not to be limited by any theory, it is believed that esters suitable for improving the filtration of oils for the purpose of separating insoluble fats from oils should contain a substrate-similar and a substrate-dissimilar moiety in the molecule. In the case of the aforementioned systems, fatty acid chains in the fats and in the sucrose ester are similar. The dextrin portion of the additive represents a polyhydric compound which is dissimilar from that of the fats.

It is also believed that it is important that materials added as filtration aids bear some relation in melting point and/ or solubility to the fats which are to be separated by filtration. These aids should be made with fatty acids having neither too high nor too low a melting point, so that the modifier will have a tendency to deposit on the incipient crystal nuclei as they are formed, thereby modifying the fat crystals. This results in the formation of crystal aggregates (around a crystallization center) which are compact and not feathery and are more easily filtered.

Further, it is believed that if the additive has too high a melting point or too low a solubility in the oil, nuclei of additive will tend to form before the fat nuclei are formed, and the additive may act as a nucleating agent for the fat, forming more nuclei than would normally appear in the fat. As a result the fat crystal aggregates will be more numerous and filtration will be more diflicult.

Although specific examples have been given to illustrate the invention, it is to be understood that the invention is not to be limited to these examples, and that variations in the processing conditions which will suggest themselves to those skilled in the art are intended to be within the scope of the invention. It will further be appreciated that dextrin ester used in commercial practice usually will be a mixture of various esters and that the specified proportions of fatty acids represent average values for such mixtures.

This is a continuation-in-part of application Serial No. 841,008, filed September 21, .1959.

What is claimed is:

1. The method of separating insoluble fatty material from glyceride oil which comprises the steps of dissolving in said glyceride oil, at a temperature at which substantially all of said fatty material is in solution, from about 0.001% to 1.0%, by weight of oil, of dextrin esterified with an average, per glucose unit, of at least one saturated fatty acid having from 13 to 22 carbon atoms in the alkyl chain and from 0 to 2 saturated fatty acids having from 1 to 5 carbon atoms in the alkyl chain; cooling the glyceride oil to a temperature at which insoluble fatty material comes out of solution; and separating the insoluble fatty material from the oil.

2. The method according to claim 1 wherein the dextrin ester is partially esterified with saturated long-chain fatty acid and contains additionally, per glucose unit, at least one saturated short-chain fatty acid having from 1 to 5 carbon atoms in the alkyl chain.

3. The method according to claim v1 wherein a solution of dextrin ester in oil is heated to a temperature at which substantially all of the insoluble fatty material is dissolved, the dextrin ester is dissolved in said heated oil, and the resulting mixture is thereafter slowly cooled to a temperature at which fatty crystals will form.

4. The method according to claim 1 wherein the oil is heated to a temperature at which substantially all of the insoluble fatty material is dissolved, the dextrin ester is dissolved in said heated oil, and the resulting mixture is slowly cooled to a temperature at which fatty crystals will form.

5. The method according to claim 1 wherein the ester comprises dextrin monopalmitate.

6. The method according to claim 1 wherein the ester comprises dextrin dipalmitate.

7. The method according to claim 1 wherein the ester is dextrin tripahnitate.

.8. The method according to claim 1 wherein the ester comprises dextrin monoacetoyl dipalmitate.

9. The method according to claim 1 wherein the oil is cottonseed oil.

10. The method according to claim 1 wherein the oil is hydrogenated soybean oil.

1:1. The method according to claim 1 wherein the oil is a directed rearranged glyceride oil.

No references cited, 

1. THE METHOD OF SEPARATING INSOLUBLE FATTY MATERIAL FROM GLYCERIDE OIL WHICH COMPRISES THE STEPS OF DISSOLVING IN SAID GLYCERIDE OIL, AT A TEMPERATURE AT WHICH SUBSTANTIALLY ALL OF SAID FATTY MATERIAL IS IN SOLUTION, FROM ABOUT 0.001% TO 1.0%, BY WEIGHT OF OIL, OF DEXTRIN ESTERIFIED WITH AN AVERAGE, PER GLUCOSE UNIT, OF AT LEAST ONE SATURATED FATTY ACID HAVING FROM 13 TO 22 CARBON ATOMS IN THE ALKYL CHAIN AND FROM 0 TO 2 SATURATED FATTY ACIDS HAVING FROM 1 TO 5 CARBON ATOMS IN THE ALKYL CHAIN; COOLING THE GLYCERIDE OIL TO A TEMPERATURE AT WHICH INSOLUBLE FATTY MATERIAL COMES OUT OF SOLUTION; AND SEPARATING THE INSOLUBLE FATTY MATERIAL FROM THE OIL. 